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[S390] spinlock: check virtual cpu running status

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This patch introduces a new function that checks the running status
of a cpu in a hypervisor. This status is not virtualized, so the check
is only correct if running in an LPAR. On acquiring a spinlock, if the
cpu holding the lock is scheduled by the hypervisor, we do a busy wait
on the lock. If it is not scheduled, we yield over to that cpu.

Signed-off-by: Gerald Schaefer <gerald.schaefer@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
This commit is contained in:
Gerald Schaefer
2010-02-26 22:37:40 +01:00
committed by Martin Schwidefsky
parent 8387c736fc
commit 59b6978745
3 changed files with 80 additions and 37 deletions
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53
arch/s390/lib/spinlock.c
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@@ -43,16 +43,24 @@ void arch_spin_lock_wait(arch_spinlock_t *lp)
{
int count = spin_retry;
unsigned int cpu = ~smp_processor_id();
unsigned int owner;
while (1) {
if (count-- <= 0) {
unsigned int owner = lp->owner_cpu;
if (owner != 0)
_raw_yield_cpu(~owner);
count = spin_retry;
owner = lp->owner_cpu;
if (!owner || smp_vcpu_scheduled(~owner)) {
for (count = spin_retry; count > 0; count--) {
if (arch_spin_is_locked(lp))
continue;
if (_raw_compare_and_swap(&lp->owner_cpu, 0,
cpu) == 0)
return;
}
if (MACHINE_IS_LPAR)
continue;
}
if (arch_spin_is_locked(lp))
continue;
owner = lp->owner_cpu;
if (owner)
_raw_yield_cpu(~owner);
if (_raw_compare_and_swap(&lp->owner_cpu, 0, cpu) == 0)
return;
}
@@ -63,17 +71,27 @@ void arch_spin_lock_wait_flags(arch_spinlock_t *lp, unsigned long flags)
{
int count = spin_retry;
unsigned int cpu = ~smp_processor_id();
unsigned int owner;
local_irq_restore(flags);
while (1) {
if (count-- <= 0) {
unsigned int owner = lp->owner_cpu;
if (owner != 0)
_raw_yield_cpu(~owner);
count = spin_retry;
owner = lp->owner_cpu;
if (!owner || smp_vcpu_scheduled(~owner)) {
for (count = spin_retry; count > 0; count--) {
if (arch_spin_is_locked(lp))
continue;
local_irq_disable();
if (_raw_compare_and_swap(&lp->owner_cpu, 0,
cpu) == 0)
return;
local_irq_restore(flags);
}
if (MACHINE_IS_LPAR)
continue;
}
if (arch_spin_is_locked(lp))
continue;
owner = lp->owner_cpu;
if (owner)
_raw_yield_cpu(~owner);
local_irq_disable();
if (_raw_compare_and_swap(&lp->owner_cpu, 0, cpu) == 0)
return;
@@ -100,8 +118,11 @@ EXPORT_SYMBOL(arch_spin_trylock_retry);
void arch_spin_relax(arch_spinlock_t *lock)
{
unsigned int cpu = lock->owner_cpu;
if (cpu != 0)
_raw_yield_cpu(~cpu);
if (cpu != 0) {
if (MACHINE_IS_VM || MACHINE_IS_KVM ||
!smp_vcpu_scheduled(~cpu))
_raw_yield_cpu(~cpu);
}
}
EXPORT_SYMBOL(arch_spin_relax);